SCImago Journal Rank (
SJR indicator) is a measure of scientific influence of scholarly journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where such citations come from. SJR indicator is a variant of the
eigenvector centrality measure used in network theory, such measure establish the importance of a node in a network based on the principle that connections to high-scoring nodes contribute more to the score of the node. The SJR indicator, which is inspired in the
PageRank algorithm, has been developed to be used in extremely large and heterogeneous journal citation networks. It is a size-independent indicator and its values order journals by its “average prestige per article” so it can be used for journal comparisons in science evaluation processes.
The
SJR indicator is an
open access journal metric which provides an alternative to
impact factor (IF) which is based on
Scopus data and uses an algorithm similar to
PageRank.
Rationale
If scientific impact is considered relating to the number of endorsements, in the form of citations, a journal receive, then prestige can be understood as a combination of such number of endorsements and the prestige or importance of the journals issuing them. SJR indicator set different values to citations depending on the importance of the journals where they are granted. This way, citations coming from highly important journals will be more valuable and hence will provide more prestige to the journals receiving its citations.
Computation
SJR indicator computation is carried out using an iterative scheme that distributes prestige values among the journals until a steady-sate solution is reached. The SJR algorithm begins by setting an identical amount of prestige to each journal, then using an iterative process, such prestige is redistributed in a process where journals transfer its achieved prestige to each other through citations. The process ends up when the difference between journal prestige values in consecutive iterations do not reach a threshold value.
The process is developed in two phases, (a) the computation of
Prestige SJR (
PSJR) for each journal: a size-dependent measure that reflects the whole journal prestige, and (b) the normalization of such measure to achieve a size-independent measure of prestige, the
SJR indicator.
See also
